Cambrian

 

 

CAMBRIAN
Beginning 541.0 million years ago
End 485.4 million years ago
 

The first period of the Phanerozoic, Cambrian, was established by British geologist Adam Sedgwick in 1835. Its name comes from the province of Cambria, located in North Wales on the British Isles.

 

Paleogeography

The beginning of the Cambrian saw the breakup of the supercontinent Pannotia into smaller continental blocks: Gondwana, Laurentia, and Baltica.

Around the equator on the continental shelves, carbonate rocks and evaporites were deposited. More north and south of the equator, up to the polar, sands were more dominant. Clays formed in the ocean depths. At the end of the Cambrian, the tectonic movements led to the beginning of the Caledonian orogeny.

 

Climate

The early Cambrian was relatively cool, but not cold enough to form new ice sheets. As the temperature rose, the remnants of the Precambrian glaciers melted, leading to large areas of continents being flooded. Numerous warm seas formed, flourishing with life.

 

Life on Earth

"The cambrian explosion"

The flooding of the continents, changes in water chemistry, and increase in oxygen levels initiated the diversification of life in the Cambrian seas. On the other hand, there was very little life on the land, limited mostly to algae mats on the banks of water bodies.

 

Skeletons

Animals gained the ability to produce mineral skeletons —carbonate shells, chitin carapaces, and other hard parts. The skeleton made it possible for animals to develop more advanced and complex body structures and increase in size. It also protected them against damage and predators, and after death, were more easily preserved as fossils.

 

Cambrian reefs

The Cambrian reefs were formed by extinct archaeocytes, animals similar to sponges. These reefs were inhabited by early arthropods, molluscs, brachiopods, and echinoderms. The most striking of these were the chitin-armoured arthropods, trilobites.

 

Chordates

Most of the main groups of animals appeared in the Cambrian, representatives of which live to this day. Among them were chordates, ancestors of vertebrates, which include us.

 

Do you know...

Cambrian saw the first appearance of predators (one of the largest being Anomalocaris), starting an arms race between the predators and the prey.